Recoilless practice cartridge

ABSTRACT

The recoilless practice cartridge is to be fired from the subcaliber barrel insert of a recoilless firearm and is provided with a projectile having a rearwardly opening central bore communicating with radial bores opening against an annular propellant charge surrounding a portion of the projectile. The practice cartridge case is provided with a bottom piece having one or more bores for receiving a detonator for ignition the propellant charge by passing a flame through the bores of the projectile and for thereafter conducting the propellant gas rearwardly through the cartridge case to counteract the recoil of firing the projectile from the cartridge case. Tamping means are provided for the propellant charge on the projectile and for the bottom piece bores.

PATENTEU FEB 1 i972 SHEET 1 BF 2 INVENTORS HEINZ GAWLICK RUDOLF STAHLMANN BY (2.7 s nzuz' ATTORNEYS PATENTEDFEB 1m 3338.571

SHEET 2 0F 2 INVENTORS HEINZ GAWLlCK RUDOLF STAHLMANN BY (7 ATTORNEYS RECOILLESS PRACTICE CARTRIDGE BACKGROUND OF THE INVENTION In guns and mortars, it is conventional to fire subcaliber practice cartridges with the aid of a barrel insert, which barrel insert can optionally also be disposed in a normal caliber dummy projectile shaped in accordance with live ammunition. When such practice cartridges are fired, a recoil effect is produced in the firearm because the cartridge and the barrel of the firearm are closed at least at the moment of firing so that the gas pressure of the propellant charge may not escape rearwardly; therefore,-this type of ammunition may not be satisfactorily used for practice firing from recoilless firearms.

In the case of a recoilless antitank firearm, particularly a bazooka, a dummy projectile having the external shape of the live, self-propelling projectile, has a subcaliber barrel for firing the practice subcaliber ammunition. An additional charge is provided at the rear of the subcaliber case threadedly engaging the dummy projectile and in a special casing disposed externally of the dummy projectile for ejecting the dummy projectile from the firearm in the firing direction.

SUMMARY OF THE INVENTION Similar to the above-known devices, the present invention relates to the firing of a subcaliber practice projectile from recoilless firearms. However, the present invention'employs a subcaliber barrel insert disposed in the firearm and provided with a practice cartridge chamber formed at its rear end; that is, the present invention does not employ a dummy projectile resembling the live ammunition. To be fired from the subcaliber barrel insert, the present invention employs a practice cartridge having a tail-stabilized projectile disposed therein. The projectile is provided with a central axially extending bore opening rearwardly and in communication at its front end, by means of radial bores, with the propellant charge behind the head of the projectile and around the projectile tail section. The bottom of the cartridge case extends rearwardly and is provided with at least one bore aligned with the projectile axial bore for transferring ignition from a detonator received within the bottom piece. Preferably, the bottom piece has a further bore branching off from its first-mentioned bore to receivethe detonator.

The barrel insert is of such a construction that its cartridge chamber allows the bottom piece of the practice cartridge to extend the chamber in the rearward direction. With ignition of the detonator, the ignition jet first proceeds from the bottom piece through the axial bore of the projectile and, by way of the radial channels, into the propellant charge chamber to ignite the propellant charge. Once the gases evolving from the ignition of the propellant charge have filled the available space and produced a sufficiently high pressure in the chamber, the projectile of the cartridge is set into motion, that is, driven forwardly out of the cartridge case and barrel insert. Simultaneously, a portion of the propellant gases flows rearwardly and escapes rearwardly through the bore or bores in the bottom piece of the practice cartridge case. With a suitable choice of design parameters, particularly dimensioning of the various components, it is possible to control the firing conditions so that any recoil of the firearm is negligible or avoided completely. The absence of recoil is desirable not only for simulating the firing of live ammunition in a recoilless rifle, but also with respect to safety because of sights disposed directly in front of the eyes of the person firing the firearm. Moreover, the rearward flash of the propellant gases exiting through the rear end of the firearm serves the useful purpose of drawing the shooter's attention to the danger of rearwardly projecting gases, which danger is considerably greater with the firing of live ammunition.

In order to Prevent the propellant gases from escaping rearwardly before a sufficiently high pressure has built up for firing of the projectile, the bore of the cartridge case bottom piece serving for the recoil escape of the propellant gases is provided with a tamping means to resist escape at least until a predetermined pressure has been reached. Insofar as the bore in the bottom piece of the cartridge case receiving the detonator is to serve simultaneously as the escape aperture for the propellant gases, additional tamping means will not be needed, because the detonator itself will effectively serve as tamping means until the buildup of the desired predetermined pressure, for example, the primer cap may serve as the tamping means. If a strong rearward-ejection of the tamping means, particularly the detonator case, is undesirable, the present invention employs one or more branched bores with a destructible tamping ring thereover on the outside. Preferably, these additional branched bores are provided radially so that the escaping propellant gases will impinge on the barrel of the firearm and thereafter flow rearwardly without any danger.

It is particularly desirable to construct the extension of the bottom piece of the cartridge case as a separate component and to secure the bottom piece through the remainder of the cartridge case by a threaded portion. With such an arrangement, the extension or bottom piece may be reused with a new cartridge case, by inserting a new detonator and optionally, attaching a new tamping ring, if the old case should not be reusable. Also, such a construction simplifies the manufacture of the practice cartridge case.

The present invention also provides a further embodiment wherein the bottom piece extension is provided with a lateral branched bore having therein a radially extending pin for receiving therein the detonator. The pin is secured in the bottom piece by means of a central axially extending setscrew. Preferably, the pin will extend through lateral bores in the barrel of the firearm to fixedly secure the practice cartridge within the firearm.

BRIEF DESCRIPTION OF THE DRAWING Further objects, features and advantages of the present invention will become more clear from the following detailed description of the drawing, wherein:

FIG. 1 is an axial cross-sectional view taken through a practice cartridge according to the present invention;

FIG. 2 is an axial cross-sectional view taken through the cartridge chamber of a firearm having therein the barrel insert and practice cartridge of the present invention, on a reduced scale with respect to FIG. 1', and

FIG. 3 is an enlarged view similar to FIG. 2, but showing a modified practice cartridge according to the present invention.

As shown in FIG. 1, the recoilless practice cartridge of the present invention is provided with a projectile having a head 2, a tail 3 and stabilizing rear fins 4, which projectile is received within the generally tubular practice cartridge case 1. The practice cartridge case 1 is provided with a bottom piece having a rearward extension 6, which is threadedly received within the rear end 5 of the remainder of the cartridge case. The projectile is provided with a rearwardly opening central axially extending bore 7 aligned with the central axially extending bore 8 in the bottom piece 6. A plurality of additional radially extending bores 9 branch off from the central bore 8. Inserted in the rear end of the bore 8, there is a detonator 10, preferably having a primer and a booster charge in combination. The radial bores 9 are tamped on the outside by means of a ring 11, preferably of synthetic material. The front end of the tail section 3 of the projectile is provided with radially extending bores 12, which provide communicationbetween the central bore 7 and the propellant charge chamber 13 directly adjacent the annular propellant charge 14 disposed around the tail section 3 directly behind the head 2. The propellant charge 14 is rearwardly tamped by means of an annular plate 20 secured to the projectile by means of a tongue and groove connection.

A signaling charge 15, for example a smoke charge, is provided with a detonating device 16, 17 and a lock mechanism 18, which is all of a bipartite construction and disposed in the head 2 of the projectile. The desired center of gravity is accurately obtained by means of the insert 19 in the head 2 of the projectile.

AS shown in FIG. 2, the practice cartridge according to FIG. 1 is shown in the cartridge chamber 26 of the barrel insert 25. The practice cartridge has an annular collar 21 provided on the extension of the bottom piece 6 to engage the annular shoulder 22 of the barrel insert 25, which insert 25 is fixedly secured with the barrel 24 of the firearm cartridge chamber by means of a spacer ring 23. With such an arrangement, the extension 6, although free, is disposed along its entire length within the barrel 24 of the firearm.

When firing the device, the ignition jet produced by the detonator 10 will travel from the bore 8 through the bore 7 axially and radially through the bores 12 to ignite the propellant charge 14. A satisfactory ignition of the propellant charge 14 is obtained within the restricted propellant charge chamber because of the tamping annular plate 20. After a predetermined propellant gas pressure has been obtained forwardly of the tamping plate 20, the tamping plate is destroyed so that the propellant gases may occupy the entire space or chamber formed rearwardly of the head 2 between the projectile and the cartridge case 1. After a predetermined pressure has been reached, the projectile will be set into motion with respect to the cartridge case 1. Simultaneously with movement of the projectile, after the tamping 1 1 has been destroyed, a portion of the propellant gases will flow through'the bores 9 and into the space 27 rearwardly of the barrel insert 25, so that these escaping propellant gases will first impinge radially upon the barrel 24 of the firearm and thereafter exit rearwardly, without any danger, to counteract the recoil of the exiting projectile so that a recoilless firing is obtained.

Although advantageous in own right, the signaling charge with its detonating device and lock in the head 2 of the projectile is not a specific part of the present invention and is therefore not described in great detail. It is contemplated that the head 2 may carry instruments or other charges, for example a tracer or flare charge; particularly, the tracer or flare charge may be provided in the front portion of the bore 7 of the projectile so that after the tracer charge has been ignited it will either remain in place or slide due to the acceleration of the practice projectile up to an abutment at the tail end where it will be held by means of air flowing into the bore 7 through the radial bores 12 during flight of the projectile.

As shown in FIG. 3, the bottom piece of the practice projectile may-be modified by providing a radial bore in the extension of the bottom piece 6 for receiving therein a radially extending pin 29. The pin 29 will project on both sides through radial bores 30 in the barrel 24 of the firearm to fixedly secure the practice projectile within the firearm. A bore 31 is provided radially within the pin 29 and receives therein a detonator 10. The pin is securely positioned by means of its annular shoulder 32 engaging a similarly formed portion of the bottom piece extension 6, or vice versa, and by means of an axially extending setscrew 33. An additional detonator or booster 34 is provided within the bore 8 of the bottom piece extension 6, which additional detonator 34 is ignited by means of the detonator l0, and in turn will ignite the propellant charge 14. A spacer ring 35 is provided between an annular flange of the firearm barrel 24 and the pin 29, to reinforce the wall of the barrel 24 and support the pin 29 with respect to the rear end of the firearm. The remaining portions of the practice projectile shown in FIG. 3 correspond with those previously described with respect to the practice projectile of FIGS. 1 and 2.

Although several embodiments have been shown and described in detail for purposes of illustration and are preferred, it is contemplated that further modifications, embodiments and variations may be made within the spirit and scope of the present invention.

It is claimed:

1. A practice cartridge insertable in a cartridge chamber for firing from a subcaliber barrel insert of recoilless firearm, comprising: a generally tubular practice cartridge case; a practice projectile axially received within said cartridge case; said practice projectile having an axially extending, rearwardly opening, generally central bore; said practice projectile having a head engaging with said cartridge case to provide a propellant gas expansion chamber between said cartridge case and said practice projectile rearwardly of said head; a propellant charge within said propellant gas expansion chamber; a destructible annular plate being provided in the cartridge case for rearwardly supporting said propellant charge on the head side of said practice projectile; said practice projectile having radial passage means providing gas communication between said projectile bore and said projectile charge; said cartridge case having a bottom piece at its rear end longitudinally spaced from said annular plate and provided with second passage means disposed therein in such a manner that, after the practice cartridge has been inserted in the cartridge chamber, the second passage means are located outside of the cartridge chamber for conducting propellant gases produced by ignition of said propellant charge from said propellant gas expansion chamber to the exterior of said cartridge for expansion rearwardly to counteract the recoil produced by firing the practice projectile forwardly out of said practice cartridge; and detonator means in said second passage means for igniting said propellant charge.

2. The cartridge according to claim 1, wherein said cartridge case includes a tubular sidewall portion with an interiorly threaded rear end, and said bottom piece having a front portion exteriorly threaded into said tubular sidewall portion rear end.

3. The cartridge according to claim 2, wherein said second passage means includes a central axially extending bottom piece bore aligned with said projectile axially extending bore, and an additional bore radially extending between said bottom piece bore and the exterior of said bottom piece; said detonator means being received within said bottom piece axially extending bore; and tamping means exteriorly covering said additional bore to retard the flow of propellant gases radially through said additional bore only until a predetermined propellant gas pressure is obtained that is substantially less than the maximum propellant gas pressure.

4. The practice cartridge according to claim 2, said bottom piece including a radially extending bore; a radially extending pin received within said bottom piece radially extending bore and being provided with a radial bore partially forming said second passage means; said detonator means being mounted in said pin radial bore.

5. The cartridge according to claim 4, wherein said pin has means for engaging the firearm to rigidly secure said cartridge in the firearm.

6. The cartridge according to claim 4, wherein said bottom piece includes an axially extending setscrew means engaging said pin preventing relative movement between said pin and said bottom means.

7. The cartridge according to claim 6, wherein said pin has means for engaging the firearm to rigidly secure said cartridge in the firearm.

8. The cartridge according to claim 1, wherein said second passage means includes a central axially extending bottom piece bore aligned with said projectile axially extending bore, and an additional bore radially extending between said bottom piece bore and the exterior of said bottom piece; said detonator means being received within said bottom piece axially ex tending bore; and tamping means exteriorly covering said additional bore to retard the flow of propellant gases radially through said additional bore only until a predetermined propellant gas pressure is obtained that is substantially less than the maximum propellant gas pressure.

9. The cartridge according to claim 1, said bottom piece including a radially extending bore; a radially extending pin received within said bottom piece radially extending bore and being provided with a radial bore partially forming said second passage means; said detonator means being mounted in said pin radial bore.

10. The cartridge according to claim 4, wherein said bottom piece includes an axially extending setscrew means engaging said pin preventing relative movement between said pin and said bottom means.

, 11. The cartridge according to claim 1, wherein said second passage means includes a central axially extending bottom piece bore aligned with said projectile axially extending bore, and an additional bore radially extending between said bottom piece bore and the exterior of said bottom piece; said detonator means being received within said bottom piece axially extending bore; and an annular synthetic tamping ring exteriorly covering said additional bore to retard the flow of propellant gases radially through said additional bore only until a predetermined propellant gas pressure is obtained that is substantially less than the maximum propellant gas pressure.

10 jectile; said second passage means including at least one bottom piece axially extending bore aligned with said projectile bore and an additional bore branching off from said bottom piece bore; sand said detonator means being in one of said bottom piece bore and said additional bore. 

1. A practice cartridge insertable in a cartridge chamber for firing from a subcaliber barrel insert of recoilless firearm, comprising: a generally tubular practice cartridge case; a practice projectile axially received within said cartridge case; said practice projectile having an axially extending, rearwardly opening, generally central bore; said practice projectile having a head engaging with said cartridge case to provide a propellant gas expansion chamber between said cartridge case and said practice projectile rearwardly of said head; a propellant charge within said propellant gas expansion chamber; a destructible annular plate being provided in the cartridge case for rearwardly supporting said propellant charge on the head side of said practice projectile; said practice projectile having radial passage means providing gas communication between said projectile bore and said projectile charge; said cartridge case having a bottom piece at its rear end longitudinally spaced from said annular plate and provided with second passage means disposed therein in such a manner that, after the practice cartridge has been inserted in the cartridge chamber, the second passage means are located outside of the cartridge chamber for conducting propellant gases produced by ignition of said propellant charge from said propellant gas expansion chamber to the exterior of said cartridge for expansion rearwardly to counteract the recoil produced by firing the practice projectile forwardly out of said practice cartridge; and detonator means in said second passage means for igniting said propellant charge.
 2. The cartridge according to claim 1, wherein said cartridge case includes a tubular sidewall portion with an interiorly threaded rear end, and said bottom piece having a front portion exteriorly threaded into said tubular sidewall portion rear end.
 3. The cartridge according to claim 2, wherein said second passage means includes a central axially extending bottom piece bore aligned with said projectile axially extending bore, and an additional bore radially extending between said bottom piece bore and the exterior of said bottom piece; said detonator means being received within said bottom piece axially extending bore; and tamping means exteriorly covering said additional bore to retard the flow of propeLlant gases radially through said additional bore only until a predetermined propellant gas pressure is obtained that is substantially less than the maximum propellant gas pressure.
 4. The practice cartridge according to claim 2, said bottom piece including a radially extending bore; a radially extending pin received within said bottom piece radially extending bore and being provided with a radial bore partially forming said second passage means; said detonator means being mounted in said pin radial bore.
 5. The cartridge according to claim 4, wherein said pin has means for engaging the firearm to rigidly secure said cartridge in the firearm.
 6. The cartridge according to claim 4, wherein said bottom piece includes an axially extending setscrew means engaging said pin preventing relative movement between said pin and said bottom means.
 7. The cartridge according to claim 6, wherein said pin has means for engaging the firearm to rigidly secure said cartridge in the firearm.
 8. The cartridge according to claim 1, wherein said second passage means includes a central axially extending bottom piece bore aligned with said projectile axially extending bore, and an additional bore radially extending between said bottom piece bore and the exterior of said bottom piece; said detonator means being received within said bottom piece axially extending bore; and tamping means exteriorly covering said additional bore to retard the flow of propellant gases radially through said additional bore only until a predetermined propellant gas pressure is obtained that is substantially less than the maximum propellant gas pressure.
 9. The cartridge according to claim 1, said bottom piece including a radially extending bore; a radially extending pin received within said bottom piece radially extending bore and being provided with a radial bore partially forming said second passage means; said detonator means being mounted in said pin radial bore.
 10. The cartridge according to claim 4, wherein said bottom piece includes an axially extending setscrew means engaging said pin preventing relative movement between said pin and said bottom means.
 11. The cartridge according to claim 1, wherein said second passage means includes a central axially extending bottom piece bore aligned with said projectile axially extending bore, and an additional bore radially extending between said bottom piece bore and the exterior of said bottom piece; said detonator means being received within said bottom piece axially extending bore; and an annular synthetic tamping ring exteriorly covering said additional bore to retard the flow of propellant gases radially through said additional bore only until a predetermined propellant gas pressure is obtained that is substantially less than the maximum propellant gas pressure.
 12. The cartridge according to claim 1, said projectile including an annular tamping plate rearwardly abutting said propellant charge and constituting means for preventing rearward movement of the propellant gases produced by ignition of said propellant charge only until the attainment of a predetermined propellant gas pressure.
 13. The cartridge according to claim 1, wherein said practice projectile has a rear stabilizing fin assembly; said propellant charge being annular and surrounding said practice projectile; said second passage means including at least one bottom piece axially extending bore aligned with said projectile bore and an additional bore branching off from said bottom piece bore; sand said detonator means being in one of said bottom piece bore and said additional bore. 